JP4950226B2 - Lighting device and lighting system for stimulating plant growth - Google Patents

Description

Explanation

  The present invention relates to a lighting device for stimulating plant growth, comprising at least one solid-state light source, suitable for emitting light of at least one wavelength within a predetermined wavelength range, at least one solid The light source is adapted for connection to an electrical network.

  The photosynthesis process for plant growth in deep red light is based on absorption of light having a peak wavelength of 662 nm by chlorophyll A and absorption of light having a peak wavelength of 642 nm by chlorophyll B. In general, red light emitting diodes (LEDs) have the highest efficiency among LEDs, ie, a relatively high radiant power per watt, and unradiated power is converted to heat.

  However, the light output of a red LED decreases dramatically with increasing temperature at the junction, i.e. with increasing temperature at the junction of the PN semiconductor material of the LED. For this reason, the LEDs are mostly mounted on the cooling element.

  It has been shown that with increasing temperature of the LED semiconductor junction from 20 ° C. to 75 ° C., the light output decreases due to at least two factors.

  In particular, red LEDs of the AlGaInP (aluminum indium gallium phosphide) type are considerably more sensitive to temperature changes than, for example, green and blue LEDs of the InGaN (indium potassium nitride) type, for example. The advantage of the AlGaInP LED material is that it has a very long lifetime, i.e. under normal conditions such a material has a lifetime of 100,000 hours.

  Japanese patent applications JP2003009662 and JP2004113160, and US Patent Publication US6921182 describe the application of LEDs for plant growth. In particular, red LEDs are used. In all of these patent publications, low power LEDs are used, in this case approximately 60 mW of power. The temperature of these LED carriers may rise rapidly, and as a result, the efficiency and scope of application is much lower than current assimilated lighting with gas discharge lamps adapted to plant growth. For example, to replace the task of a 600W standard sodium lamp, 10,000 such LEDs must be used.

  Therefore, large scale application of LEDs in greenhouses requires a fairly large number of power LEDs of 0.5W or larger. Such LEDs generate a large amount of heat. Therefore, the carrier for such an LED is provided with a portion adapted to radiate the heat generated by the power LED. A well-known technique for semiconductor cooling is to mount the LEDs on the plate so that the LED makes a good thermal connection with the plate. The plate is then connected to a device that can radiate the absorbed heat. In such a heat release system, the generated heat is conducted to a place for heat radiation by a plate using heat conduction and later dissipated to the surroundings using heat dissipation. Such a thermal radiation system reduces the temperature of the carrier, which is generally still insufficient.

  The present invention aims to provide more efficient thermal radiation for lighting devices that stimulate plant growth compared to state-of-the-art devices.

Accordingly, an illumination device according to the invention is characterized in that at least one solid state light source is in contact with a cooling medium, and in one embodiment, the cooling medium is between −50 ° C. and 0 ° C. Preferably, it has a temperature in the temperature range between −50 ° C. and −20 ° C. Thus, the lighting device comprises a cooled solid light source. Cooling the light source improves the efficiency of the lighting device. In one embodiment, the lighting device is further provided with a first tube, wherein at least a portion of the first tube is transparent to light from a predetermined wavelength range, and the at least one A solid light source is positioned in the first tube. Such positioning of the at least one solid state light source provides further protection.

In one embodiment thereof, the first tube is suitable for receiving a cooling medium, and the first tube is provided with a supply opening and a discharge opening for supplying and discharging the cooling medium, respectively. ing. The lighting device is further provided with a second tube having a larger diameter than the first tube, and the second tube is positioned to surround the first tube. The second tube is at least partially transparent to light from a predetermined wavelength range. In this embodiment, at least one light source is directly cooled by the cooling medium. The space between the first and second tubes, for example, such as nitrogen, is filled with a suitable inert gas, it is possible to prevent the formation of condensation or ice.

  In another embodiment thereof, the lighting device is further provided with a third tube having a smaller diameter than the first tube, and positioned such that the third tube is surrounded by the first tube. It has been. The third tube is a metal tube suitable for receiving a cooling medium, and the third tube is provided with a supply opening and a discharge opening for supplying and discharging the cooling medium, respectively. Here, at least one solid state light source is positioned in contact with the third tube between the first and third tubes. Unlike the previous embodiment, there is no direct contact between the at least one solid light source and the cooling medium, and in particular, the connection of at least one solid light source is soldered. In some cases, the cooling medium prevents dissolution of the connection of at least one solid light source. Such dissolution may cause a rupture of the connection or may cause the cooling medium to become turbid. The third tube may include a metal such as copper and / or aluminum. Such a metal is an excellent conductor and the third tube can reliably serve as an electrical connection. Thus, the third tube may form a first connection of at least one light source with the electrical network. In such a case, the lighting device may further be provided with a strip of metal, the strip of metal being electrically isolated from the third tube, the strip of metal with the electrical network; A second connection of at least one light source is formed.

  In both embodiments described above, the lighting device may further comprise spacing means for maintaining the first tube at a predetermined distance with respect to the second tube or the third tube. In this way, the tubes may be aligned in a controlled manner relative to each other.

  The at least one solid state light source may be an LED. Such a light source may be positioned in the vicinity of the plant without reaching very high temperatures due to dissipation. The LED may have an opening angle between 30 ° and 90 °. This angle offers the possibility of guiding the emitted light. The LED may be mounted on a ceramic substrate.

  A light source that is very often chosen in the present invention is a light source suitable for emitting light between 640 and 700 nm, such as a red LED. In particular, the optimum temperature for the function of such an LED is in the range between −40 ° C. and −20 ° C. Suitable cooling media include carbon dioxide and alcohol.

  The invention further relates to a lighting system for stimulating plant growth in a greenhouse, wherein the lighting system has a plurality of lighting devices according to one of the above-described embodiments having more than one tube, and inputs and outputs. And a cooling system adapted to cool the cooling medium. Here, the tubes in the plurality of lighting devices adapted to receive and transport the cooling medium form a circulation channel in contact with the input and output of the cooling system, for each lighting device of the plurality of lighting devices. At least one solid state light source is electrically connected in parallel to each other.

  The invention further relates to a method of manufacturing a lighting device as described above, the method comprising providing a first tube and providing at least one of a second tube and a third tube. Positioning the first tube with respect to at least one of the second tube and the third tube, whereby one of both tubes is surrounded by the other tube, Introducing spacing means between them to fix the mutual position of both tubes and the at least one solid light source to the first tube so that the at least one solid light source is in contact with the cooling medium When the lighting device is used, the cooling medium is located in one of both tubes.

  In one embodiment thereof, providing the tube, positioning the first tube with respect to at least one of the second tube and the third tube, introducing the spacing means, extruding. Is done at the same time.

Finally, the present invention further relates to a method of using the lighting device as described above, the method, - the temperature in the temperature range between 50 ° C. and -20 ° C., and cooling the at least one light source It is characterized by that.

  In the following, the invention is further described by way of example with reference to the drawings. The drawings are not intended to limit the scope of the invention, but merely illustrate the invention.

  FIG. 1 shows a graph in which the relative light output of an LED is plotted as a function of temperature on the semiconductor junction in the LED. From this graph, for the types of LEDs shown, namely red (dotted line), red-orange (gray solid line), and amber (black solid line), the output of light is the junction point of the semiconductor, It seems to decrease rapidly with the temperature of the junction point. However, from the graph in FIG. 1, it may be concluded that when the temperature is lowered, especially at temperatures below 20 ° C., the light output increases rapidly.

FIG. 2 shows a cross-sectional view of a first embodiment of a lighting device according to the present invention. The lighting device comprises a cooling device that cools at least one solid state light source, for example one or more LEDs 6. The cooling device comprises an inner tube 1 and an outer tube 2, both tubes 1 and 2 being transparent to the light emitted by one or more LEDs. The inner tube 1 and the outer tube 2 are connected to each other using contacts 5 of a spacing means such as, for example, a spacing disk 4. Here, the contact 5 is preferably in contact with the inner tube 1 at a certain distance. The inner tube 1 is partially or totally filled with a cooling medium, which is a cooling liquid having a suitable solidification temperature, such as, for example, glycol, alcohol or liquid carbon dioxide (CO ₂ ). Or a gas, for example (CO ₂ ) gas or air. In the inner tube 1, one or more LEDs 6, hereinafter simply referred to as LEDs 6, are positioned, which may be positioned to be freely connected in the inner tube 1. The LED 6 is part of an electrical circuit that provides adequate ambient lighting and in particular stimulates plant growth.

  The LED 6 preferably has an opening angle of 30 ° to 90 °. Due to the limited aperture angle, the light produced by the LED can be directed almost exclusively to the crop, thus limiting the amount of light that does not reach the crop to a minimum. In determining the optimum aperture angle, the fact that the intensity of the radiated power increases with the square of the decrease in aperture angle may be taken into account.

  In view of the low temperature of the cooling medium, the LED 6 in the cooling medium is positioned as shown in FIG. 2, and a carrier 7 for the LED 6 that can be used as an additional cooling element is not strictly necessary. In order to prevent condensation or ice formation on the inner tube 1, the cavity 8 between the inner tube 1 and the outer tube 2 can be filled with a suitable inert gas, for example nitrogen. The contact 5 between the inner tube 1 and the outer tube 2 must be as small as possible in order to minimize heat loss due to heat transfer.

  In FIG. 2, a spacing disc 4 is shown as a spacing means, which comprises a contact 5 that contacts the inner tube 1 and contacts the outer tube 2. However, as is known to those skilled in the art, it is also possible to design a spacing disc with a contact 5 that contacts the outer tube 2 and contacts the inner tube 1.

  In this embodiment, not only the electrical connection between the LEDs, but also the connection to the external electrical network is formed by a cascade connection using conductive wires, for example copper.

  FIG. 3 shows a cross-sectional view of a second embodiment of a lighting device according to the present invention, which includes cooling for cooling at least one solid state light source, for example one or more LEDs 6. A device is provided. This cooling device also comprises an inner tube 1 and an outer tube 2, both tubes 1 and 2 being transparent to the light emitted by the LED 6. Again, the inner tube 1 and the outer tube 2 may be connected to each other using contacts 5 of a spacing means such as a spacing disk 4, for example. Here, the contact 5 is preferably in contact with the inner tube 1 at a certain distance.

Unlike the lighting device shown in FIG. 2, the LED 6, which will be referred to below as the LED circuit 10 and forms part of the electrical circuit, is mounted on the metal cooling tube 11. The metal of the metal cooling tube 11 may include a material such as copper (Cu) and / or aluminum (Al). The LED circuit 8 can be mounted directly on the metal cooling tube 11 using a solder connection. However, it is also possible to mount the LED circuit 10 on a ceramic strip or ceramic substrate that has a printed circuit and is in contact with the metal cooling tube 11. For example, a cooling medium, such as a coolant or a cooled gas, flows through the cooling tube. The cooling medium is, for example, cooled CO ₂ gas.

In addition to providing cooling, the metal cooling tube 11 may further operate as an electrical cable for the first connection of the LED circuit 10 to an electrical network (not shown). The metal cooling tube 11 needs to be thick enough because, in many applications, such as shining a large number of plants in a greenhouse, relatively large power is required. Due to the size of the greenhouse, currents of 100 amps or higher are no exception. As a rough guide, it can be said that a 10 ampere per 1 mm ² cross section can be processed for a copper cable. At low temperatures such as −30 ° C., the resistivity is low, for example at −30 ° C. it is approximately 25% lower than the resistivity at room temperature. Therefore, at this temperature, at least 12.5 amperes per mm ² should be considered. As is the case here, if the tube is more actively cooled, it is possible to handle a higher current density, for example 25 A / mm ² .

  In this embodiment of the lighting device, only the LED circuit 8 on the cooling tube 11 is cooled, for example to a temperature of −30 ° C., so that the remaining space in the inner tube 1 of the cooling device is, for example, nitrogen. It can be filled with a suitable gas or with an insulating bubble, such as polyurethane, except in the line of sight, ie where there is light from the LED. Especially when the cooling medium is related to the cooling liquid, the lighting device as shown in FIG. 3 has the advantage that there is no direct contact between the LED and the cooling medium. In that case, the connection parts of the LEDs are more likely to dissolve in the cooling medium, especially if they are soldered, resulting in a rupture of the connection or turbidity of the cooling medium. Furthermore, the lighting device shown in FIG. 3 provides better thermal insulation than the lighting device shown in FIG.

  In the lighting device shown in FIGS. 2 and 3, separate components or combinations of components such as, for example, a combination of an inner tube 1, an outer tube 2 and one or more distance disks 4 are extruded. Can be formed using molding. Of course, the inner tube 1 and the outer tube 2 may be formed separately and subsequently slid into each other. Whether an embodiment with one or two tube parts is chosen depends on the amount of contraction / expansion change absorbed along the entire length of the respective cooling element.

  FIG. 4 shows in detail the possible connections between the LED circuit 10 and the metal cooling tube 11 in the embodiment shown in FIG. With the connections shown in FIG. 4, the LED circuit 10 is further connected to an electrical network (not shown) via a second electrical connection. For example, the second electrical connection has the form of a metal strip 15, for example of copper and / or aluminum. In order to ensure that there is a galvanic separation between the first electrical connection, i.e. the metal cooling tube 11 and the second electrical connection, for example a suitable plastic, electrical Insulating clip 16 is introduced between both connections 11,15. Plastic electrically insulating clips 16 can also be manufactured using an extrusion technique.

In many applications it is convenient if one or more of the different tubes 1, 2, 11 are constructed from tube elements. In the lighting device shown in FIG. 3, the metal cooling tube 11 may be formed by coupling cooling tube elements. In addition, this connection provides a conductive connection. The metal cooling tube 11 is connected to an electrical network (not shown) that operates with, for example, 22V direct current or alternating current. The metal cooling tube 11 forms a first electrical connection with one or more LED circuits 8. The second electrical connection may be applied in the same way as described above. Again, the thickness of the metal cooling tube 11 depends on the current and material forces used. A sufficiently thick metal cooling tube 11 is required when using a large amount of power by using an electrically parallel coupling of several coupling elements. As described above, as a rough guide, it can be said that a flow of 10 amperes per 1 mm ² cross section can be processed for a copper tube. At low temperatures such as −30 ° C., the resistivity is low, for example at −30 ° C. it is approximately 25% lower. Therefore, at this temperature, at least 12.5 amperes per mm ² should be considered. As is the case here, if the tube is more actively cooled, it is possible to handle a higher current density, for example 25 A / mm ² .

  FIG. 5 shows a side view of the lighting device shown in FIG. 3, wherein the metal cooling tube 11 comprises different cooling tube elements 11a, 11b. Furthermore, in the embodiment shown, the inner tube 1 and the outer tube 2 are divided into segments. The cross-sectional view shown in FIG. 3 can be made with a cross-section through the lighting device according to line III-III.

  In FIG. 5, it is also shown that the different cooling tube elements 11a, 11b are joined together by means of joining. The coupling of the cooling tube elements 11a, 11b and hence the connection of the LED circuits 10a, 10b connected to the cooling tube elements 11a, 11b, respectively, are adapted, for example, at the end of the cooling tube elements 11a, 11b. This can be realized by using different shapes.

  In the case shown in FIG. 5, the metal cooling tube elements 11a and 11b are as shown in FIG. Next, from the end corresponding to the area B surrounded in FIG. 4, for example, a portion of approximately 2 cm is removed from these cooling tube elements 11a and 11b. The remaining substantially rounded ends can then be coupled together using, for example, a conductive coupling tube. In that case, the ends of the cooling tube elements 11a, 11b are moved towards each other as indicated by the arrows in FIG. 5 until the cooling tube elements 11a, 11b contact. Next, the cooling tube elements 11a and 11b can be tightened to have pressure resistance by one or more fastening means such as a hose clip, for example. In this way, several types of connections can be formed. Therefore, the slit shown between the cooling tube elements 11a, 11b does not exist in such a connection when it is not desirable for the cooling medium to leak to the surroundings.

  A first type of coupling 31 causes one of the one or more hose clips to be electrically connected to the electrical network to provide the electrical network and the first electrical connection 22 as described with respect to FIG. Connected to. As described with respect to FIG. 4, a metal strip 15 is attached to the LED circuits 10 a, 10 b by fastening means, such as screws 20, in order to provide an electrical network and a second electrical connection 23. It has been. In a similar manner, further cooling tube elements 11a, 11b may be coupled together. Bonding occurs by appropriate bonding with metal seals, such as, for example, copper and rubber. By properly insulating the entire connection of the bond, the formation of ice and / or frost may be prevented by a suitable insulator material 21 such as, for example, polyurethane. Unlike what is shown in FIG. 5, it is clear that the metal strips 15 may be connected to each other, like the cooling tube elements 11a, 11b. However, such connections are not shown to avoid confusion with respect to other elements.

  A second type of connection 32 (not shown separately) connects the two cooling tube elements 11a, 11b to each other in the same way as shown in FIG. However, in this type there is no direct connection with the electrical network. On the other hand, the metal strip 15 is connected to the LED circuit 10a, and the metal strip 15 is electrically connected to the LED circuit. Since the cooling tube elements 11a, 11b are both conductive, they are also electrically connected in parallel.

  For a third type of coupling 33, i.e. a series of cooling tube elements coupled to each other, for termination coupling, termination elements can be used, as shown in FIG. 2 is suitable for coupling to one or more insulated connection hoses 25, and is suitable for coupling to one or more insulated connection hoses 25; Suitable for connection to the electrical network 40 and at the other end suitable for connection to the electrical network 40. Therefore, such a termination portion is a termination portion when it is involved in an electrical supply, but when it is involved in cooling, as known to those skilled in the art, and as shown in FIG. Since it is necessary to circulate the cooling medium, it is not a terminal part.

  It is preferable that the other electric cables 26 and 27 are thermally insulated sufficiently so that the loss does not occur as much as possible due to the contact of the cooling tube elements 11a and 11b with the other electric cables 26 and 27.

  FIG. 7 shows a lighting system for stimulating plant growth in a greenhouse, comprising the lighting device embodiment described above. Thus, the lighting system comprises a series of coupled cooling tube elements 11a, 11b. As can be seen, there are all types of couplings 31, 32, 33 described above. The illumination system further comprises a cooling system 41 adapted to cool the cooling medium. The cooling system 41 is provided with at least one input and at least one output. Cooling tube elements such as the cooling tube elements 11a, 11b are connected in series with each other so that the cooling tube element contacts at least one input and at least one output of the cooling system to form a circulation channel. . It should be noted that the LED circuits 10a, 10b are also electrically connected in parallel with respect to each other.

  The LED circuit 10 can be realized in several ways. Some considerations given in the following description may play a role in the selection of certain embodiments of LED circuit 10. In order to stay within the electrical safety zone, the use of a low voltage is preferred, for example 24V or lower. The photosynthesis process for plant growth in deep red light is based on absorption of light having a peak wavelength of 662 nm by chlorophyll A and absorption of light having a peak wavelength of 642 nm by chlorophyll B. Therefore, the use of LEDs that produce such wavelengths is preferred. In order to generate sufficient light, LEDs with high luminescence are particularly suitable. An example of such an LED is a so-called power LED.

  The average voltage of the red power LED is 2.2 volts. Therefore, ten red power LEDs can be connected in series when using a 22 volt (DC or AC) voltage. In order to prevent a very large load in the rearward direction in the lighting device described above, it is preferred that the LEDs can be connected in a series bridge with respect to the connection to an alternating voltage.

  By coupling the cooling tube elements described above, a series circuit is automatically formed and the separate cooling elements are automatically electrically connected in parallel.

  FIG. 8 shows a schematic diagram of a possible LED circuit 10. In this LED circuit 10, 60 LEDs are connected by a bridge. Using a 0.77W power LED, the standard current through the power LED reaches 350mA, and at a voltage of 22 volts and a current of 2.1 amperes, the generated power of 46.2W in one cooling element. Bring. Depending on the length of the cooling tube elements 11a, 11b, it is possible to realize a 231 W or larger circuit in a single cooling tube element 11a, 11b.

As described in Dutch patent application 1027960, connected LED bridges result in circuits that increase circuit reliability and lifetime. Furthermore, for many chemical processes, the lifetime increases roughly three times for each temperature drop of 10 ° C. The fact that a chemical reaction involving an aging process proceeds at a speed proportional to the following value is used.

Where T is the temperature in Kelvin, k is the Boltzmann constant (gas constant R divided by Avogadro's number), and ΔH is the activation energy.

  As can be read in US Pat. No. 6,921,182, suitable configurations of LEDs that promote plant growth have a red LED emitting light between 600 nm and 700 nm and a wavelength of approximately 470 nm. It is a combination with a blue LED that emits light. Here, the ratio of red light is larger than the ratio of blue light. As an alternative to blue LEDs, possibly gas discharge lamps can also be used. Blue LEDs are not only less efficient than red LEDs, but are also much less sensitive to temperature. The amount of thermal energy applied to the cooling device described above disturbs the efficiency of the device. The blue LED is preferably applied in a separate electrical circuit other than the cooling system with the red LED.

At wavelengths between 600 and 700 nm, the visible portion of the emitted energy is considerably less than the light emitted by a sodium growth lamp, for example, mostly 580 nm. The perceivable lumen light output at several wavelengths according to the “C. I. E. photopic luminous efficiency function 1988” is listed in Table 1.

From Table 1 it can be seen that at 630 nm, the perceivable light output reaches only 26.5% of the perceivable light output in daylight. At 660 nm this is additionally 6.1%, and at 690 nm only 1% of the appreciable light output in daylight is obtained.

  Lamps for assimilation lighting in greenhouses are aimed at additional lighting for short days in addition to normal daylight. In many cases, the amount needed for growth is already absorbed from daylight, so blue light can be omitted. Furthermore, red LEDs are very suitable for obtaining plant flowering.

  In particular, in densely populated areas such as the Netherlands, an important aspect is that growing light can cause considerable light pollution. Therefore, legal regulations apply to the amount of light that can be perceived outside the greenhouse.

  As can be seen from Table 1, a red LED having a wavelength of 690 nm only emits 1% visible light when using the same amount of radiated electromagnetic force as an LED having a shorter wavelength.

  As previously mentioned for photosynthesis, a spectral distribution in the 600-700 nm range is necessary for optimal chlorophyll A and B absorption.

Furthermore, the best distribution of LEDs with several wavelengths depends on the type of crop. For example, the NASA (USA) study provides the following results, which are incorporated in Table 2.

Most of the CO ₂ is converted and the highest amount of biomass (biomass) appears to be produced at wavelengths between 640 nm and 690 nm. Beyond 690 nm, both CO ₂ conversion (photosynthesis) and produced biomass rapidly decrease. At 705 nm, both processes are almost negligible. In a suitable combination configuration of LEDs having several wavelengths, a preferred combination of LEDs, so-called LED modules, can be obtained, in which the ratio of LEDs having a wavelength of approximately 662 nm, ie the maximum absorption wavelength for chlorophyll. Has been shown to account for approximately 75% of the total number of LEDs covering the red spectrum of 640-700 nm.

When choosing the optimal combination of LEDs, i.e. when constructing an LED module, the fact that the main wavelength of the LED shifts as a result of lowering temperature should be taken into account. For a red LED, the wavelength shift Δλ relative to the shift ΔT _{j at} the LED junction temperature is approximately 0.05 Δλ / ΔT _j nm / ° C. Therefore, reducing the junction temperature by 50 ° C., ΔT _j = 50, results in a wavelength shift of radiation Δλ of 2.5 nm in the direction of shorter wavelengths.

  LED modules configured according to the above criteria have been shown to emit twice as much electromagnetic (light) energy when cooled to a temperature of about −30 ° C. At such temperatures, with proper selection of red LEDs, about 50% of this electromagnetic (light) energy is converted to light and 50% is converted to heat.

  When applied as assimilation lighting in a greenhouse, depending on the size of the greenhouse, thousands of LEDs may be required. If all LEDs are operated at a voltage of 2.2V and a current of 350 mA, the generated power reaches 0.77 W per LED. Thus, in generating a percentage of conversion as described above, ie 50% light, 50% heat, at a temperature of −30 ° C., half of these 0.77 W is the heat pump as generated heat Need to be dissipated using. Cooling to −30 ° C. at an ambient temperature of 30 ° C. results in a temperature difference ΔT of 60 ° C. According to the second law of thermodynamics, approximately 22% of the thermal energy is required to remove heat. Thus, when using 1000 LEDs, this theoretically corresponds to 22% of 385 watts = 85 watts. A cooling device for removing such power can be designed by an average person skilled in the art using techniques known in cryogenic technology. Therefore, it will not be further explained.

  LEDs offer the possibility of directing light exactly where light is needed, but directing light where light is needed is commonly used, such as high pressure sodium lamps It is much more difficult with prior art assimilated lighting.

  Such a lamp has an energy consumption of 400 to 600W. Due to the heat generated by these lamps, these lamps must remain at a considerable distance above the crop, for example, a minimum of 180 cm, to prevent crop burning.

  Furthermore, the intensity of the electromagnetic radiation that shines on the crop increases with the square of the distance between the light source and the crop. Therefore, when using high pressure sodium lamps, the fact that they are placed at a greater distance with respect to the crops will lead to less effective lighting of these crops. Much of the energy generated for growth will shed light on places adjacent to crops.

  Unlike a high pressure sodium lamp, the LED may be positioned directly above the crop and may later move with the growth of the crop using replacement techniques known to the average person skilled in the art. Therefore, more efficient crop lighting can be obtained.

  In addition, optimal elements such as lenses and mirrors can be used to direct the light from the LED to a specific location. Therefore, it is possible to guide light to an area that is difficult to reach.

The above description describes only a number of possible embodiments of the invention. Many alternative embodiments of the invention can be envisaged and it is easy to recognize that many alternative embodiments are configured within the scope of the invention. These are defined by the claims .

FIG. 1 shows a graph in which the relative light output of an LED is plotted as a function of temperature on a semiconductor junction in the LED. FIG. 2 shows a cross-sectional view of a first embodiment of a lighting device according to the present invention. FIG. 3 shows a cross-sectional view of a second embodiment of a lighting device according to the present invention. FIG. 4 shows details of the embodiment of the lighting device shown in FIG. FIG. 5 shows a side view of the type of coupling of the cooling tube elements in the embodiment of the lighting device shown in FIG. FIG. 6 shows the type of coupling of the cooling tube elements and the connecting hose shown in FIG. FIG. 7 shows a lighting system comprising an embodiment of a lighting device. FIG. 8 shows a schematic diagram of a possible LED circuit for use in the present invention.

Claims (19)

A lighting device for stimulating the growth of plants,
At least one solid state light source suitable for emitting light of at least one wavelength within a predetermined wavelength range and adapted for connection to an electrical network;
A first tube that is at least partially transparent to light within the predetermined wavelength range;
A second tube having a smaller diameter than the first tube and positioned to be surrounded by the first tube;
The at least one solid state light source is positioned in the first tube;
The second tube is a metal tube suitable for receiving a cooling medium, and provided with a supply opening and a discharge opening for supplying and discharging the cooling medium, respectively;
Wherein at least one solid state light source, between said first and said second tube, said has been positioned to be in contact with the second tube, whereby said at least one solid state light source, wherein lighting devices that are in contact with the cooling medium.   The lighting device according to claim 1, wherein the cooling medium has a temperature in a temperature range between −50 ° C. and 0 ° C. Before SL and the third tube is further provided with a larger diameter than the first tube and the third tube are positioned so as to surround the first tube,
Said third tube, the lighting device according to claim 1 or 2, wherein the relative light from a predetermined wavelength range, at least partially transparent. The lighting device according to claim 3, wherein a cavity between the first tube and the third tube is filled with an inert gas. The lighting device according to claim 1, wherein the metal of the second tube includes copper and / or aluminum. 6. The lighting device according to any one of claims 1 to 5, wherein the second tube forms a first connection of the at least one light source with the electrical network. The lighting device is further provided with a strip of metal,
The lighting device of claim 6 , wherein the metal strip is electrically isolated from the second tube and forms a second connection of the electrical network and the at least one light source. The lighting device before Symbol the respect third tube, the lighting device according to any one of claims 3 to 7 further comprising spacing means for maintaining the first tube at a defined distance is in advance. Wherein at least one solid state light sources, the lighting device of any one of claims 1 to 8 an LED. The lighting device of claim 9, wherein the at least one LED is adapted to emit light with an opening angle between 30 ° and 90 °. The at least one LED is in contact with the cooling medium through a substrate;
The substrate, according to claim 9 or 10 lighting device according contain ceramic. The lighting device according to any one of claims 1 to 11 , wherein the cooling medium has a temperature in a temperature range between -40 ° C and -20 ° C. The lighting device according to any one of claims 1 to 12 , wherein the predetermined wavelength is in a range between 640 and 700 nm. The cooling medium, carbon dioxide and, glycol, alcohol and at least one claims 1 contains to 13 lighting device according to any one of of the. In a lighting system that stimulates plant growth in the greenhouse,
A plurality of lighting devices according to any one of claims 1 to 14 ,
A cooling system adapted to cool the cooling medium provided with inputs and outputs;
Tubes in the plurality of lighting devices adapted to receive and transfer the cooling medium are connected in series with each other so that the tubes in the plurality of lighting devices are of the cooling system. Forming a circulation channel in contact with the input and output,
The lighting system, wherein the at least one solid state light source for each lighting device of the plurality of lighting devices is electrically connected in parallel to each other. 15. A method of manufacturing a lighting device according to any one of claims 1 to 14 ,
The method
Providing a first tube;
A second tube having a smaller diameter than the first tube is provided, the second tube being a metal tube suitable for receiving a cooling medium, and for supplying and discharging the cooling medium, respectively. A supply opening and a discharge opening are provided,
Positioning the first tube with respect to the second tube such that the second tube is surrounded by the first tube;
When the lighting device is used, the at least one solid light source is positioned between the tubes, contacts the second tube, and contacts the cooling medium. Positioning . Providing a third tube having a larger diameter than the first tube, the third tube being at least partially transparent to light from the predetermined wavelength range;
Positioning the third tube such that the third tube surrounds the first tube;
The method of claim 16, further comprising introducing spacing means between the first tube and the third tube to fix their mutual position. Providing the first tube, providing the third tube, positioning the third tube with respect to the first tube , and introducing the spacing means are extrusion molding. 18. The method of claim 17, wherein the method is performed simultaneously using A method of using an illumination device according to any one of 請 Motomeko 1 to 14,
The method includes cooling the at least one light source to a temperature in a temperature range between −50 ° C. and −20 ° C.

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